# ZB.MOM.WW.Health

Health-check libraries for the **ZB.MOM.WW SCADA family** (OtOpcUa, MxAccessGateway, ScadaBridge). These are **libraries, not a service** — each package is linked directly into the consuming application at build time. There is no central health process or network hop; probes run in-process alongside the application.

The library normalizes the three-tier health endpoint convention (`/health/ready`, `/health/active`, `/healthz`) and provides reusable probe implementations so the three sister projects share a common surface without duplicating probe logic.

---

## Packages

| Package | Description | Key Dependencies |
|---|---|---|
| `ZB.MOM.WW.Health` | Core tiers, `MapZbHealth` extension, canonical JSON writer (`ZbHealthWriter`), `IActiveNodeGate` seam, `GrpcDependencyHealthCheck` reachability probe, and tier-tag constants (`ZbHealthTags`). No Akka or EF dependency. | `Microsoft.AspNetCore.App` (framework ref), `Grpc.Net.Client` |
| `ZB.MOM.WW.Health.Akka` | `AkkaClusterHealthCheck` with a configurable `AkkaClusterStatusPolicy` (presets: `Default` three-way / `OtOpcUaCompat` two-way), `ActiveNodeHealthCheck` with an optional role filter, and `AkkaActiveNodeGate` that backs `IActiveNodeGate` from the cluster member state. | `ZB.MOM.WW.Health`, `Akka.Cluster` |
| `ZB.MOM.WW.Health.EntityFrameworkCore` | `DatabaseHealthCheck<TContext>` with `CanConnectAsync` by default and an optional `ProbeQuery` delegate for custom connectivity validation. | `ZB.MOM.WW.Health`, `Microsoft.EntityFrameworkCore` |

---

## Consumer Matrix

| Consumer | `ZB.MOM.WW.Health` (core) | `ZB.MOM.WW.Health.Akka` | `ZB.MOM.WW.Health.EntityFrameworkCore` |
|---|:---:|:---:|:---:|
| **OtOpcUa** | yes (+ `GrpcDependencyHealthCheck` for the MxAccessGateway channel) | yes | yes |
| **MxAccessGateway** | yes (+ `GrpcDependencyHealthCheck` for the x86 worker IPC) | — | — |
| **ScadaBridge** | yes | yes | yes |

MxAccessGateway consumes the core package only — it has no Akka cluster and no EF DbContext. OtOpcUa and ScadaBridge consume all three packages.

---

## Versioning

All three packages are versioned **lockstep** from `Directory.Build.props`. The current release is **0.2.0**. A single version bump in `Directory.Build.props` bumps all three packages simultaneously — consumers should reference the same version for all ZB.MOM.WW.Health packages.

### 0.2.0 — per-entry `data` (additive, non-breaking)

- `ZbHealthWriter` emits an optional `"data": { … }` object per entry, sourced from the check's
  `HealthCheckResult.Data`, **only when non-empty** — a check that publishes no data produces a
  byte-identical body to 0.1.0, so every existing consumer is unaffected. Data keys are written
  verbatim (the camelCase policy applies to the envelope, not to dictionary keys).
- `AkkaClusterHealthCheck` populates that dictionary with this node's cluster view: `leader`
  (omitted while unknown), `selfAddress`, `selfRoles`, `memberCount`, `unreachableCount`. The
  startup-safety paths (no `ActorSystem`, cluster not yet accessible) stay description-only.
- Consumers gain the leader field on a package bump alone — no application code change, provided the
  app registers the shared `AkkaClusterHealthCheck`.

---

## Building and testing

```bash
# from ZB.MOM.WW.Health/
dotnet build ZB.MOM.WW.Health.slnx
dotnet test  ZB.MOM.WW.Health.slnx
```

All three test assemblies run with `dotnet test` and require no external dependencies — no database and no
external cluster (the cluster-data tests form a single-node in-process Akka cluster on a loopback port
via `Akka.TestKit.Xunit2`):

| Assembly | Tests |
|---|---|
| `ZB.MOM.WW.Health.Tests` | 25 |
| `ZB.MOM.WW.Health.Akka.Tests` | 39 |
| `ZB.MOM.WW.Health.EntityFrameworkCore.Tests` | 6 |
| **Total** | **70** |

---

## Packing

```bash
dotnet pack ZB.MOM.WW.Health.slnx -c Release -o ./artifacts
```

Produces three `.nupkg` files in `artifacts/`:

```
ZB.MOM.WW.Health.0.2.0.nupkg
ZB.MOM.WW.Health.Akka.0.2.0.nupkg
ZB.MOM.WW.Health.EntityFrameworkCore.0.2.0.nupkg
```

`GeneratePackageOnBuild` is off — pack explicitly as above.

---

## Status

**Built at 0.2.0 and published to the Gitea NuGet feed. Adopted by all four apps** (OtOpcUa, MxAccessGateway, ScadaBridge, HistorianGateway). Adoption is tracked in the component backlog:

- `~/Desktop/scadaproj/components/health/GAPS.md`

Design documentation lives alongside that backlog:

- `~/Desktop/scadaproj/components/health/spec/SPEC.md` — normalized three-tier target
- `~/Desktop/scadaproj/components/health/shared-contract/ZB.MOM.WW.Health.md` — proposed API
- `~/Desktop/scadaproj/components/health/current-state/` — per-project current state (code-verified)
